There is a common mentality among many people that condemnation of sinful activity that a person engages in is equivalent to rejection of the person committing that sin.
Thus, disapproval of "trendy" sins such as homosexual activity is often taken to be a sign that one hates a person. The words “judge ye not” (Matt 7:1) are used to attack Christians who condemn homosexual behavior as evil.
But condemning a sinful behavior is not a sign that one disapproves of a person. On the contrary, condemning a sinner is known as admonishing the sinner in Catholic theology, and as such is a measure of love.
Because humans are fallen creatures, we want to allow others to be able commit certain sins, because we want to be "free" to commit our own favorite sins. And for this reason, we are leery of admonishing the sinner.
But if a friend is about to commit murder, it is not “love” to allow him to wield a knife against his intended victim. If a friend is committing suicide, it is not “love” to let them pull the trigger of a gun and blow their brains out. On the contrary, it would show a lack of love NOT to stop one's friend from doing evil activity.
All sin is destructive to the person committing that sin. All sin poisons the lives of both the sinner and the people around the sinner.
Since sin is so destructive, it is not “love” to let someone remain in their sin – no matter how minor. Instead, we as Christians are called to warn those who commit sin that they are harming themselves.
Admonishment of a sinner is a spiritual work of mercy by the Church for this very reason.
I wrote in a previous post that God loves His creatures with a burning love that demands that His creatures be perfect. As He does with us, so we must do with others. In a spirit of loving, Christian charity, we must correct our brethren when they do wrong.